There is currently a need to move mobilized robots, forklift trucks, mobilized platforms or pallets, light earth moving equipment, mobile chairs for disabled persons and other vehicles utilized in industrial, military, police, research, medical and other applications with complete flexibility in three degrees of freedom. This permits the vehicle to (a) be moved from any existing position, at any angle of heading through a full 360.degree., (b) be turned in either direction through a full 360.degree. about a substantially fixed axis perpendicular to the surface on which the vehicle is moving; and (c) be moved in any desired continuous trajectory on a surface from the starting position. Such a vehicle could be utilized alone in some applications, or could be connected as a base or foot to a larger device, for example, a robotic device, which is adapted to perform various functions either while being moved by the device of this invention or at various locations where the robot is moved by the device of this invention. With such additional robotic device, movement of an object in six degrees of freedom is possible.
While many devices are currently available for moving vehicles, including robots, to a desired position, there is only one device currently available which provides full flexibility of motion in three degrees of freedom. This is a device developed in Sweden using what is referred to as "the Mecanum wheel". Each Mecanum wheel has a plurality of angled rollers extending around its periphery. By controlling the rotation of all the wheels (normally a standard four wheels) on the vehicle, movement in a desired direction ma be achieved.
However, with this device, forward and sideway motions are coupled leading to a complex control system. The device also requires high friction for omnidirectional capability and has limited load carrying capacity because of the fact that loads are supported on slender roller spindles. The device also has limited capability to negotiate adverse terrain.
A need therefore exists for an improved omnidirectional vehicle which provides full range of motion in three degrees of freedom with a relatively simple control system. Such device should also be usable over varying degrees of adverse terrain, and should distribute the weight of the vehicle over many relatively strong points of contact so as to maximize weight carrying capacity.
Another related problem is to be able to move a work surface in three degrees of freedom relatively easily so that work may be performed thereon. Again, devices for performing such function easily and inexpensively do not readily exist. Except for the fact that the stationary member and the moving member are reversed in such application, the problems to be overcome are substantially the same.